For the Dynavoice archives:  I had misread John Tuttle's note about
suction for a regular player piano as 4 _feet_ instead of 4 _inches_
for normal volume.  This explains why the PPCo or other vacuum boxes
do not solve the noise problem for the Dynavoice.

Because of the relatively small surface area acted upon by outside
pressure on the Dynavoice bellows (only about 1 square inch), the
Dynavoice requires about 30" of vacuum for normal volume, and can
handle up to about 4 feet (48") for really loud.  Just about any
turbine ticking along at 4" suction is going to be fairly quiet and
easily muffled.  Two and one-half to four feet suction is another
matter entirely, and generates an awful lot of racket in the turbine.

The best solution is to utilize an external vacuum source.  Real
external -- like about a block away!

Tom Lear
San Francisco CA